Handpiece assemblies are available on the market in which channels for cooling air and cooling water are formed in the headpiece, which lead to the tool-side face of the headpiece. These channels lead out of the headpiece housing on the handgrip side at axially spaced points, and are sealed against each other by O-rings. The handgrip housing has aligned outlets for cooling air and cooling water.
In such handpiece assemblies the headpieces are mechanically extravagent and expensive on account of the channels formed in them for the flowing media. Also, in prolonged use sealing problems arise at the point of connection to the handgrip.
Handpiece assemblies are also known in which an outlet for cooling air and an outlet for cooling water are formed in the end section of the handgrip adjoining the headpiece. In such handpiece assemblies the headpiece contains no channels for the flowing media; but it is a disadvantage that only a single outlet for cooling air and a single outlet for cooling water are available. If one works with only a single cooling spray jet there is however the risk of an excessively strong heating at the working point if this spray jet is restrained by an obstruction, e.g. the dental material surrounding the drilling hole.
The present invention is intended to provide a dental handpiece assembly, by which two geometrically non-equivalent spray jets of a cooling water/cooling air mixture are obtained, without needing to provide channels for the flowing media in the headpiece.
With the development of the invention according to one variation it is achieved that the two cooling spray jets are produced close to the tool axis, but the headpiece with fitted tool can still easily be withdrawn in the axial direction and slipped on on account of the fork-like shape of the handgrip end.
The developments of the invention according to another embodiment are advantageous in respect of a small overall height of the headpiece and in respect of a precise positioning of the headpiece on the handgrip.
With the development of the invention according to a further embodiment, one obtains an enlarged handling area for detaching and slipping on the headpiece and a continuously flush external contour of the handpiece assembly.
With the development of the invention according to still another embodiment, a secure location of the headpiece on the handgrip is obtained without noticeable enlargement of the radial dimension of the handpiece assembly.
Known handpiece assemblies have at the headpiece end of the handgrip several light emission openings, which are supplied via light pipes with light from a bulb which is installed in the motor unit carrying the hand grip. With a handpiece assembly according to a further variation, such long light pipes, feeding through the whole handgrip, which are disadvantageous both with respect to the assembly of the handgrip and with respect to light losses, can be dispensed with. With a handpiece assembly according to this further variation, the light required for the illumination of the working point is produced in immediate proximity to the headpiece. Since the lighting bore is open towards the front end of the handgrip, the light leaving there can easily be enclosed in a light pipe which extends in an arc from here to a point which lies essentially diametrically opposite, with respect to the tool axis, to the light exit slit of the lighting bore. In this way the baseline between the two light beams referred to is enlarged and the shadowing by the tool is considerably less than by use of two light beams having only a small distance between them.
With the development of the invention according to an additional variation, a cooling of the light source is assured at only a very small additional constructional cost.
The development of the invention according to an additional embodiment is advantageous in respect of a sealing of the electrical supply line to the light source against moisture, and in respect of a simple replacement of the light source.